The waste extraction system, also known as the waste reclamation system, sewage and waste reclamation, or the sewer, was a plumbing system used to manage and process all bodily wastes aboard starships and starbases. (DS9: "Little Green Men")

On stardate 48892.1, The Doctor, while in a malfunctioning holodeck program (which he believed to be real life), requested a ship-wide system update and the computer reported sewage and waste reclamation as one of them. At the time, it was presumably offline as with almost all other systems. (VOY: "Projections")

Ira Steven Behr commented "When we first wrote the words 'waste extraction', we didn't even want to think of what the hell that was. Extraction? Whoa! That's taking twenty-fourth century technology a little far. It takes you one step past replicators. I just hope it has nothing to with sharp pincers". Waste extraction was mentioned in many more scripts in the fifth season and Behr also "saw a mention of waste extraction in one of the licensed Deep Space Ninecomic books. Finally we had to stop because it was getting ridiculous". (Star Trek: Deep Space Nine Companion, p 288)